Machines for slip-forming concrete curbing or curb and gutter in situ have long been known. Typically, such machines are moved forward along the path of pour and have a hopper for receiving wet concrete from a mixer. Such concrete drops through the hopper onto the ground and a form communicating with the rear of the hopper slides over and shapes the concrete, the intention being to leave a properly shaped integral curb-gutter of indeterminate length formed in place therebehind. However, prior slip-form machines of which I am aware have not been entirely satisfactory, for a number of reasons.
For example, in one type of prior slip-form curb and gutter machine, a tractor equipped with hydraulic lifts is required to suspend and advance the hopper and slip-form unit along the proposed path of the curb-gutter. Because of the very high cost of a conventional tractor equipped with hydraulic lifts, such machine is not suitable for many curb and gutter jobs, particularly smaller ones, and cannot compete with other more economically constructed machines. Also, the direction of the path along which the curb-gutter is laid depends on steering of the tractor and can be thrown off by momentary inattention of the driver, looseness or "play" in the tractor steering, or a previously unnoticed bump in the path of a tractor wheel. Also, since he must not only control speed, but must also steer the tractor, the operator is both poorly positioned to view, and has relatively little time to supervise, actual curb forming, including flow of concrete to the hopper, quality of the curb emerging from the slip-form, etc. Moreover, whereas it normally may be desired to suspend the hopper-slip-form unit centrally beneath the tractor, formation of a curb-gutter close-by obstructions, e.g. trees, would be prevented by the fact that a conventional tractor is much wider than a conventional curb-gutter ribbon. However, to suspend the form and hopper beside the tractor adds further cost and complication to the hydraulic lift and mounting apparatus, further distorts the operator's view of the slip-forming operation, and results in a total vehicle width which may approach or exceed local or state limits for road travel from job to job.
The second basic type of prior machine does not use a tractor but rather comprises a hopper and slip-form unit supported and guided for advancement atop a pair of fixed guides laid in spaced parallel relation on the ground along the path of curb-gutter pour. Typically, such guides are upstanding plates and serve as fixed forms for the opposite sides of the curb-gutter ribbon, while the advancing hopper and slip-form unit is shallow and merely shapes the top of the concrete curb-gutter ribbon. However, to be practical, the fixed side forms must be much longer than the hopper and slip-form unit and must be accurately sized as to height. Also, two pair of such forms are required to permit the hopper and slip-form unit to advance from one pair to the next for continuously forming a long, in situ curb-gutter ribbon. Thus, such fixed side forms add substantially to the cost of the curb-gutter machine. Also, it is difficult and time consuming to set up such side forms since they determine the vertical angle of the finished curb gutter sides, must be a constant separation spacing, and must have their top edges at a constant preselected offset in height from each other.
Machines of this second type typically have been advanced by pulling by the concrete truck or have carried a relatively costly motor or engine for pulling the slip-form-hopper unit along guides. The former may result in yawing or jerky forward movement and divorces control of forward movement from the operator located at the slip-form unit. The latter, aside from the extra cost of the motor or engine and its transmission, tends to make the machine too heavy to be readily lifted by a typical two man curb-gutter forming crew, tends to induce unwanted misplaced vibration, and/or requires additional power supplies or electric cords on or to the slip-form and hopper unit.
Typical prior art machines of the general type above referenced may be seen for example in U.S. Pat. Nos. 3,954,359, 4,027,990, 3,208,362, 3,108,518 and 3,733,141.
Accordingly, the objects and purposes of this invention include the provision of:
1. A machine for slip-forming a concrete curb and gutter ribbon, on the site and without limitation as to continuous curb-gutter ribbon length.
2. A machine, as aforesaid, of relatively light weight and compact size, which can be transported from job to job on a conventional pick-up truck and can readily be lifted by two men onto and off of such a truck.
3. A machine, as aforesaid, including an operator support platform atop the slip-form portion of the machine, by which the weight of the machine operator assists in compacting and forming the concrete curb-gutter ribbon, while providing the operator a vantage point for close and direct observation of the entire slip-forming operation from feeding of concrete to the hopper through the action of the trailing edge of the machine in final smoothing and troweling of the concrete ribbon, and from which the operator can directly control positioning and operation of concrete flow inducing vibrator devices and can precisely control forward advance of the machine through hand winching.
4. A machine, as aforesaid, in which height and direction of machine travel is controlled simply yet precisely by support of machine wheels on two side-by-side tracks, one of which is provided with a longitudinal guide member, wherein the tracks are normally on the same level and tractor guides may be simply formed of common construction materials, and wherein machine supporting wheels are adjustable for forming small radius curved sections of curb-gutter ribbon.
5. A machine, as aforesaid, which is free of fixed side forms and in which support and guidance of the machine is independent from forming of the curb-gutter ribbon, wherein the slip-form has side walls extending downward preferably past the top of the track and which are the sole forming surfaces for the sides of the curb-gutter ribbon.
6. A machine, as aforesaid, which provides a fixed width gap for escape of air bubbles from the concrete surface just ahead of the final troweling portion of the machine and provides for vertical adjustment, as a unit, of such final trowel portion, and in which the machine may support and guide reinforcing rods into the concrete mass being poured, to produce a steel reinforced concrete ribbon.
7. A machine, as aforesaid, capable of interchangeably supporting different cross-section slip-forms and trowel units for forming curbs, gutters, or combination curb-gutter ribbons of any desired cross-sectional shape, and in which the machine can be converted from one cross-sectional configuration to another rapidly and easily, with only ordinary hand tools and without special skill.
8. A machine, as aforesaid, constructable at low cost of normally available materials without need for elaborate production machinery and capable of economically handling a wide variety of large or small slip-forming jobs, and which is capable of relatively rapid set-up and operation by only two men (e.g. an operator and a concrete chute attendant).
Other objects and purposes of this invention will be apparent to persons acquainted with apparatus of this general type upon reading the following specification and inspection of the accompanying drawings.